NaturePlus: Message List - Help to identify these neat rocks, please?http://www.nhm.ac.uk/natureplus/community/identification/fossils-rocks?view=discussions
Most recent forum messagesenThu, 25 Apr 2013 05:50:24 GMTJive SBS 4.5.6.0 (http://jivesoftware.com/products/clearspace/)2013-04-25T05:50:24ZenRe: Help to identify these neat rocks, please?http://www.nhm.ac.uk/natureplus/message/28291?tstart=0#28291
<!-- [DocumentBodyStart:2804795e-f36f-47ac-8655-7cecc623e4a7] --><div class="jive-rendered-content"><p><strong>Blue one</strong></p><p><strong>Blue agate with alteration<br/></strong></p><p>I think this is a type of cryptocrystalline quartz, which we could probably refer to as agate. The blue colour arises from impurities, and I suspect the little flecks do too - through metamorphic alteration, perhaps of the same impurities. What the flecks are is difficult to say. The opalescent parts are probably due to optical intererfence effects in thin slivers (there will be a thin crack just behind where you see the opalescence). If you look up 'Newton's rings', you'll get more of an idea about that.</p><p>Refs:</p><p>- <a class="jive-link-external-small" href="http://www.blueagates.com/">http://www.blueagates.com/</a> (regarding a blue agate deposit in Washington state)</p><p>- "Agates and Jaspers are patterned chalcedonies that are a whole study themselves, and are so diverse as to preclude proper coverage in this article, so for in depth information on them, the best book on the subject in this writers' opinion is Agates and Jaspers by Ron Gibbs" [<a class="jive-link-external-small" href="http://www.gemrockauctions.com/docs/gemstone-articles/quartz-information">http://www.gemrockauctions.com/docs/gemstone-articles/quartz-information</a>]</p><p style="min-height: 8pt; height: 8pt; padding: 0px;">&#160;</p><p style="min-height: 8pt; height: 8pt; padding: 0px;">&#160;</p><p><strong>Silvery one</strong></p><p><strong>Graphite</strong></p><p>Very nice specimen!</p><p><a class="jive-link-external-small" href="http://commons.wikimedia.org/wiki/File:Graphite_crystalline.jpg">http://commons.wikimedia.org/wiki/File:Graphite_crystalline.jpg</a></p><p>Re graphite in the Adirondacks / New York state:</p><p>- <a class="jive-link-external-small" href="http://www.miningartifacts.org/NewYorkMines.html">http://www.miningartifacts.org/NewYorkMines.html</a></p><p> - <a class="jive-link-external-small" href="http://books.google.com.cy/books/about/The_Adirondack_graphite_deposits.html?id=A6kNAAAAYAAJ&amp;redir_esc=y">http://books.google.com.cy/books/about/The_Adirondack_graphite_deposits.html?id=A6kNAAAAYAAJ&amp;redir_esc=y</a></p></div><!-- [DocumentBodyEnd:2804795e-f36f-47ac-8655-7cecc623e4a7] -->Thu, 25 Apr 2013 05:50:24 GMThttp://www.nhm.ac.uk/natureplus/message/28291?tstart=0#28291MikeHardman2013-04-25T05:50:24Z1 year, 10 months ago0Help to identify these neat rocks, please?http://www.nhm.ac.uk/natureplus/message/28289?tstart=0#28289
<!-- [DocumentBodyStart:508c09f7-a6ed-4bb0-8ee6-ab370c821f53] --><div class="jive-rendered-content"><p>Blue one: solid and hard, appears to have opalescent flecks when turned just right. On the thin edge, it is sharp and almost transparent.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;">&#160;</p><p>Grey one: very shiny and seems black until light hits it's "facets." Looks flaky but is quite solid. Lightweight.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;">&#160;</p><p>Found in the central Adirondacks of northern New York State. Thank you for looking!</p></div><!-- [DocumentBodyEnd:508c09f7-a6ed-4bb0-8ee6-ab370c821f53] -->Wed, 24 Apr 2013 23:17:07 GMThttp://www.nhm.ac.uk/natureplus/message/28289?tstart=0#28289KineticEntity2013-04-24T23:17:07Z1 year, 10 months ago10